This study of secondary prevention of drug abuse will examine the effectiveness of cognitive behavioral intervention (CBI), and a combination intervention using both CBI and Behavioral Parent Intervention (BPI)with high risk aggressive, preadolescent boys. A multiple-gating procedure will be used to identify 4th and 5th grade boys rated by both teachers & parents as having a relatively high number of aggressive behaviors. The two annual cohorts of aggressive boys will be randomly assigned to one of three conditions; cognitive behavioral intervention (CBI), combined cognitive behavioral intervention and behavioral parent intervention (CBI + BPI), and an untreated aggressive comparison group(UA). These three conditions will be compared to a nonaggressive comparison group (Comp) to determine if the identified aggressive boys move within normal ranges of dependent measures. The design will permit two follow-up assessments during the first two years after the treatment period. The CBI and BPI are derived from previous prevention and intervention research. Both of these interventions are based on models of how moderating variables (children's social cognitive processes; family interactional behavior) affect children's behaviors. The CBI is a school-based intervention that includes 46 weeks of group & individual sessions over a 1 year period. The BPI consists of an initial intensive treatment period ranging from 10 to 16 consecutive weekly sessions, followed by an open-ended follow-up behavioral assessment, and children's reports of self-esteem. The longitudinal design will asses the secondary prevention effects of the interventions. Since childhood aggression has been identified as a risk marker for later drug use, successfully treated aggressive boys should also display a lower incidence of drug use at the follow-up periods. In addition, the direct effects of interventions on boys' drug use and behavioral changes will be determined. Finally, the relationship between boys' behavior change and boys' initial levels of social cognitive processes and family moderating variables will be examined, and the relationship between changes over time on these sets of variables will be assessed. These analyses will further understanding of child and family characteristics which predict drug use and prevention outcomes, and will permit testing of the relationship between the models of moderating variables, boys' behavior, and boys' drug use.